P. Goldenberg, P. Lewis, and J O'Keefe, representation and
the development of a process understanding of function, in E.
Dubinsky and G. Harel, eds., the Concept of Function (MAA Notes,
vol. 5), MAA, 1992, 235-260
Larry Gonick, The Cartoon Guide to Calculus (Cartoon
Guides) (Paperback, HarperCollins, 2012).
J.E. Graver, A Geometric approach to linear functions, College
Mathematics Journal 26:5 (1995) 389-394.
Sherman Stein and Anthony Barcellos , Calculus and
Analytic Geometry, 5th Edition (McGraw-Hill, 1992)
James Stewart, Calculus: Early Transcendentals, 7th
Edition (2012, Brooks/Cole, Cengage Learning) See page A 43.
H. Swann and J. Johnson, Prof. E. McSquared's Calculus Primer,
William Kaufmann, Inc., Part I, 1975; Part II, 1976; Second
Edition; 1978; Expanded Intergalactic Version, Janson
Publications, 1989; Reprinted by Dyer & Swann Publications,
2002. Link to google.com/books/reader